‘73 dart swinger 3 speed manual trans convert to 4 speed
Would a 63 thru 66 model have a trunion shaft?
Up to 65 was trunion for sure, 66 I can't recall, 67 was slip yoke but no more 3.09 low.
________________________________________________________________
I got my stuff from Passon Performance; the gear set, his aluminum box and cover, and the M/S. Then I slammed it all together, BEST gearset I've ever had, and I've had them all! Works great with a 230/110 cam and 10.9Scr with aluminum heads, and 3.55s.
Worked just as good with a 223/110 cam, and that one could easily pull 3.23s.
I did not yet have it with my 292/108 cam, but I think it would have been dynomite. As it was that combo liked a starter gear of about 11 or 12, which was 4.30 gear with the standard ratio.
If I would have had the 3.09 with that one, the rear gear coulda been 3.73s.
These were all for hi-perf street duty.
My opinion is tho, to have a second gear that is reved right out with your combo, at about 60/65 mph.
With a 230* cam peaking at about 5300, the shift rpm in my combo is about 5800. With 27" tires, this calls for a second gear road-ratio of 7.53. Working the math in reverse, this calls for one of the following second/differential combos;
B) 1.67x4.51 ,rounds to 4.56s, comes in the Overdrive box
C) 1.77x4.25, rounds to 4.30s, comes in the T/A box
A) 1.92x3.92, rounds to 3.91s, comes in the 2.66/3.09box
If you had a different combo with less power at a lower rpm than my engine makes, then you might choose to sync 60/65 with say 5250rpm, and that would require 5250/5800= .905 as much gear, or 3.55s, with the A combo. See how that works? There's no sense in running much over 3.55s with that combo, because; A) first gear will just go up in smoke, and B) to get to 60/65mph, you will be out of the powerband in second gear, and it will want to be shifted early, and you lose, and C) of these rear gears;which are you gonna want to cruise with?
Again this is for a streeter.
But you could work the formulas backwards from say 62.5 mph. Say you wanted 3.55s to be your maximum rear-gear. What cam would be best for low-ET at 62.5mph? Well 62.5 calls for 5300rpm in 1.92 second gear with a 27" tire, and those 3.55s. So now you just build a motor with as much power as you need to satisfy your personal ET requirement at 5300 rpm. To put a lil more average power down, you might put the powerpeak at 5000 rpm.
But say you had that overdrive trans with a 1.67 second gear. 62.5 now calls for a power peak at 4600, with those 3.55s. And yer gonna need more than a 360 to make a good showing at 4600rpm. See how that Works?
But say you wanted to be even quicker, so you sacrifice hiway mileage and opt for 3.91s. To make this work, the powerpeak now needs to be 5800 with the 1.92 second gear, or 5100 with the 1.67 second/overdrive box.
__________________________________________________
Now,just to piss you off,
my second roadgear is 8.56, which calls for a powerpeak of 6650.lol. I actually don't care about low-ET at 62.5mph.... because...... it's still spinning those crappy 295/50-15 Cooper Cobras......... or the 325/50-15 BFG DragRadials for that matter.
Happy HotRodding
I bet you're wondering about how I get a second gear of 8.56.lol. Well that is actually first over with a GVOD, or 3.55x3.09x.78=8.56 the next ratio I use is 3.55x1.92=6.82. Then 3.55x1.92x.78=5.32,again a split gear, which gets me 93mph @6150,which is what the combo does in the 1/8th mile. Yeah that's waaay past the powerpeak. Did I mention that I don't care? No really I don't. That was a one-time deal. I'm a streeter.
lol.
